Declining mortality over the past several decades has contributed to an increase in the proportion of persons over 64 in the US population, especially of persons over 84, the "oldest old." Since aging is associated with an increased incidence and prevalence of chronic disease, it is likely that the demand for medical care will steadily increase in the years ahead. However, improvements in health care and reductions in risk factors may be delaying the onset of chronic disease to ages closer to death; if this is so, the interval between onset of disease and death may be compressed, resulting in a decreased demand for medical care services. Increased survival may also be leading to increases in multiple diagnoses. Comorbidity affects treatment, survival and progression of disease. It is strongly associated with changes in functional status and mortality. Comorbidity is a central fact in understanding the epidemiology of chronic diseases in the elderly. The research includes nine-year mortality, incidence and prevalence of chronic disease, and health services use in two cohorts each composed of 3,000 Kaiser members aged 65 and over in 1971 and 1980. Only members who took the Multiphasic Health Checkup (MHC) within 5 years of the baseline date can be included in the study. Information on chronic disease diagnoses, causespecific mortality, physiological and socio-demographic risk factors, and health services utilization is being obtained from computerized hospitalization and Multiphasic Health Checkup records and from medical charts. The original study hypothesis is that the period of morbidity from onset of chronic disease to death is shorter in the 1980 cohort. Duration of morbidity is shorter because the age at onset of disease is occurring later, at ages closer to death. This hypothesis will be examined for specific conditions, especially including cardiovascular diseases and cancers. In addition, the influence of cohort differences in comorbidity on survival with chronic disease win be examined. Cohort differences in the risk of additional comorbidities among those with cardiovascular or musculoskeletal diagnoses will be examined. This continuation is being requested to allow completion of the original study analyses which have been delayed by significant budget cuts and an increase in work scope. As originally proposed, this research did not include assessment of the influence of comorbidity on cohort differences.